Hill admitted he killed 46-year-old Janice Mayhew in her apartment in 2008 and 22-year-old Sierra Sullivan at a St. Louis hotel in 2009.

It was only after Hill began writing letters to authorities while in prison for killing a woman in 2006 that investigators linked him to the additional homicides. Authorities say the letters contained details only the killer would have known.

In a March letter to a St. Louis judge, Hill blamed the killings on what he said was his mental illness.